Science: Dna Prints

A foolproof crime test

Dawn Ashworth, 15, left a friend's house last July to walk to her home in Enderby, a village in England's East Midlands. She never made it. Two days | later her body was found; she had been raped and strangled. Soon after, police arrested a 17-year-old youth in connection with that killing and an earlier, similar murder.

But three months later, convinced that the suspect was innocent of both crimes, the police freed him. How could they be so sure? By using the new technique of DNA fingerprinting, which involves analyzing nuclear rather than mitochondrial DNA, they had proved that while...